Such a belt retractor is part of an active vehicle occupant restraint system by which various precautions are taken in recognizing a critical vehicle situation, in order to protect a vehicle occupant from negative consequences in as optimum a way as possible. The steps that are taken may comprise, for example, changing the inclination of a backrest of a vehicle seat, closing vehicle windows, pre-tensioning the safety belt, and further measures. All these measures are reversible, which means that as soon as the status of the vehicle which was detected as being critical is no longer present, the vehicle is returned into its initial state again.
In belt retractors with a pre-tensioner drive, a known blocking mechanism can be activated, for example by a braking of the vehicle, when a belt spool is turned in a winding direction of the safety belt and the safety belt has been pre-tensioned. This can lead to a blocking catch, driven by the blocking mechanism, engaging fully into blocking teeth associated with it, when the belt spool is turned slightly in the unwinding direction, so that the belt spool is fully blocked. The blocking teeth are usually undercut so as to be able to reliably transfer between the blocking teeth and the blocking catch the high blocking loads which are active in the case of an accident. In order that the blocking catch can be moved out from the blocking teeth again, a back rotation of the belt spool in the winding direction is necessary. As the safety belt is in any case already pre-tensioned, the vehicle occupant feels this to be uncomfortable.
Various designs are known from the prior art, by which the undesired blocking of the belt spool is to be prevented, by the steering in of the blocking catch being prevented. In such designs, however, a comparatively complicated assembly is necessary.
The object of the invention consists in further developing a belt retractor in that an undesired steering in of the blocking catch is reliably prevented with as little effort as possible.